Missingno 0 can shiny, but missingnos 252-276 arn't shiny.
EDIT:The 0 missingno is non-leathel. but as for 252-276, I don't know.
EDIT:If you ever find a (?) named ??????????, DON'T CATCH IT! But if you find a (?) without a name or a ?? named ?, it's safe to catch em'. (You know, old NoName and ?)
Wait! How do I know all this stuff?!